Spark plug



numeral 10 indicate: a tubular body mem-' Patented Apr. l, 1924.

UNITED STATES.

PATENT OFFICE.

SPARK PLUG.

Applicationfiled April 7, 1923. Serial No. 630,553.

may be readily removed for cleaning or re-.

placement.

One object of this'invention is to provide a spark-plugof the above nature having a detachable outer annular sparking electrode within which is a detachable central sparking electrode having a reversible and interchangeable point.

A further object is to provide a sparkplug of the above nature having an ad ustable auxiliary spark gap mounted in a vis ble position to indicate to the operator whether the plug is operating or has gone dead.

A further object is to provide a sparkplug which will be relatively simple, cheap to manufacture, easy to manipulate, and very eflicient and durable in use. a With these and other objects in view, there has-been illustrated on the accompanying drawings one form in which the invention may be conveniently embodied in practice.

Fig. 1 is a sectional view of the sparkplug, taken along a longitudinal axis.

Fig. 2 .is a transverse sectional view of the spark-plug, taken along the line 22 of Flg. 1. looking in the direction of the arrows.

Fig. 3 is a transverse sectional view of the spark-plug taken along the line 33 of Fig. 1, looking in the direction of the arrows.

Referring now to the drawings in which like reference numerals denote corresponding parts throughout the several views, the

--Th e section 11 is also provided with interior threads 11, for a purpose to be hereinafter more fully described. The tapered flange 15 is ada ted to fit over an outstanding flange 16 o a dome-shaped top 17 constructed of glass or other suitable transparent material which rests upon the top of the reduced section 11, and within which is located an auxiliary intensifying spark gap to be hereinafter more fully described. The reduced lowei section 12 of the body member 10 is ro'vided with exterior threads 18 adapte' to fit within a threaded hole in the combustion chamber ofthe cylinder of an lnternallc ombustion engine. the reduced lower section 12 is threaded for a short distance at its lower end toreceive the outer annular sparking electrode 19 the lower'end of which is inwardly tapered at 20 and is provided with a flat bottom section 21, said flat section 21 having a central aperture 22 adapted to concentrically surround an inner sparking electrode 23.

' lVithin the hollow body member 10 is a metallic core rod 24 the axis of which coincides with the longitudinal axis of the body member. The core rod 24 is insulated from the body memberlO by means of a sleeve 25 of mica or other suitable insulating material, said sleeve 25 having an enlarged shoulder 26. The shoulder 26 rests on a washer 27, preferably of copper, which washer in turn rests upon an internal shoulder 28 formed in the metallic body member 10. The'insulating mica sleeve 25 is locked securely in position by a pair of annular locking disks 29 and 30 which engage the interior threads 11 of the upper reduced section 11. The central core rod 24 is provided with a threaded top portion adapted to receive a nut 31 which nut may be screwed down upon the mica sleeve 26 to press the core rod tightly against a conical shoulder 32 formed on said core rod.

The inside of The bottom portion of the core rod 24 is provided with external threads upon which a tubular cap 33, is adapted to be screwed, said tubular cap having an inwardly tapered bottom portion 34 fitting. the lower surface of a double-conical shoulder 35 formed at the mid-point of the reversible inner sparking electrode 23. The sparking electrode 23 is provided with a pair of cylindrical end portions 36, 36, preferably having the same diameter, and adapted to be interchangeably held within 'a socket 37 in the end of the core rod 24. By means of this construction, it will be evident that when one end 36 of the reversible inner sparking electrode 23 has been worn out, the electrode 23 may be readily turned around to bring the unused end into sparking position. It will also be understood that both the inner and outer sparking electrodes 23 and 19 may be read1- ly removed for cleaning or replacement.

The transparent dome-shaped top 17 is provided with a flat top having a central threaded aperture 38 within I which is screwed a tube 39. The tube 39 is provided with an enlarged bottom head 39 having sockets 40 adapted to be engaged by a suitable tool for screwing the tube up into the threaded aperture 38. The tube is threaded on both its interior and exterior surfaces, and is adapted to fit about an inner threaded metallic rod 41. The rod 41 has a knurled knob 42 at its top end, and a smooth cylindrical sparking point 43 at its lower end, said point 43 being located in alinement with a reduced point 44 on the top of the core rod 24. After the adjustable rod 41 has been screwed down into the tube 38 to the proper position, it may be held securely in place by means of' a locking nut 45 mounted on said rod 41 and engaging a collar 46 of a conducting terminal strip 47, said collar being threaded upon the outside of the tube 39. The conducting terminal strip 47 has its outer end provided with a threader binding post 48 rigidly secured to the strip 47, and having a binding nut 49 threaded thereon, the conducting ignition wire 50 being held between the nut 49 and the base of the strip 47 as clearly shown in Fig. 1. The diameter of the binding post 48 is preferably made the same as the diameter of the top of the core rod 24. By means of this construction, in case one of the transparent tops 17 should become broken, the threaded top of the core rod 24 may be employed as a substitute binding post, and the wire 50 may be held in electrical connection with said core rod by the nut 49.

A brass guard 51 is preferably provided upon the upper portion of the transparent dome-shaped top 17 in order to lessen the danger of accidental breakage of said top.

One advantage of this invention is that the auxiliary spark gap will be visible from the outside at all times. It will thus be possible for the operator to determine at a glance whether any of the spark plugs of the engine are out of order. It has also been found that the use of the auxiliary spark gap serves to intensify the spark at the main sparking electrodes.

While there has been disclosed in this specification, one form in which the invention may be embodied, it is to be understood that this form is shown for the purpose of illustration only, and that the invention is not to be limited to the specific disclosure, but may be modified and embodied in various other forms without departing from its spirit. In short, the invention includes all the modifications and embodiments coming within the scope of the following claims.

Having thus fully described the invention, what is claimed as new, and for which it is desired to secure Letters Patent, is:

1. In a spark-plug, an outer metallic supporting member adapted to project through an aperture of a combustion chamber, an

inner metallic core concentrically positioned within said supporting member, an outer annular sparking electrode secured to the bottom of said supporting member, said inher core having a central socket at its bottom end, a double-ended reversible electrode adapted to fit within said socket, said reversible electrode having a shoulder intermediate its ends, and a locking cap surrounding the bottom of said core and adapted to engage against the shoulder of said reversible electrode for holding it detachably in position.

2. In a spark-plug, an outer metallic body member adapted to seat in an aperture of a combustion chamber, an inner metallic core located within said body member and insulated therefrom, a detachable ring electrode threaded upon the bottom of said body member, said core having a socket at its lower end, a detachable reversible electrode point fitting within said socket, and having a central shoulder, and a collar on said core to engage said shoulder for releasably holding said electrode point in said socket.

3. In a spark plug, a tubular metallic body member, a metallic core located within said body member and insulated therefrom, an annular outer sparking electrode on the bottom of said tubular body member and a reversible inner sparking electrode detachably secured upon the bottom of said metallic core, said reversible electrode comprising a pair of cylindrical end sections joined by a pair of opposed central conical sectionsgg In testngt'ony whereof, I have afiixed my signature to this specification.

THOMAS F. BUTLER. 

